Medical injectors are well known in the art including syringes and pen injectors. Medical injectors typically include a plunger for advancing one or more stoppers in delivering a medicament during an injection. Although it is known in the prior art to provide syringe plungers with teeth or other features to prevent retraction and re-use after an initial injection, syringe plungers are typically actuated through direct application of linear force. Dose size is a direct function of plunger displacement. It may be difficult to control linear displacement of the plunger, thus, resulting in difficulty over control of dose size.
As for pen injectors, a lead screw or other rotating plunger is provided which is mechanically coupled to a dose-setting knob or other actuator through a series of mechanical connections. The typical pen injector mechanism is fairly complex and consists of multiple cooperating parts. For costs reasons and simplicity of use, a minimum number of working parts is desired.